I got to like level 42 without really understanding the color--I thought it was just a hitpoint indicator, so I just put bots on until they died. It did seem that some bots were better than others but not until I quit and read the description did I get it, d'oh!
But the music was cool and factory-like, nice funky jam. Would love more music/dance as part of the theme, either with beat sequencing the robots etc?
Also on web, I never did figure out the launchers or got them to work, not sure if I didn't understand or they were bugged. I just used them to bump the big guys.